The Battle of Mohi (today Muhi), also known as Battle of the Sajó River or Battle of the Tisza River (11 April 1241), was the main battle between the Mongol Empire and the Kingdom of Hungary during the Mongol invasion of Europe. It took place at Muhi, southwest of the Sajó River. After the invasion, Hungary lay in ruins. Nearly half of the inhabited places had been destroyed by the invading armies. Around 15–25 percent of the population was lost, mostly in lowland areas, especially in the Great Hungarian Plain, the southern reaches of the Hungarian plain in the area now called the Banat and in southern Transylvania.